AFL players need to make a stand and take more control of the substances put into their bodies, Port Adelaide great Warren Tredrea says.

Revealing he was offered banned substances during his stellar 14-year playing career, Tredrea said players needed to ask more questions of club doctors after Essendon became embroiled in an unprecedented investigation by the AFL and the Australian Sports Anti-Doping Authority investigation into the use of supplements last season.

"Clubs should have a responsibility to act in the best interests of their players," he said.

"But now more than ever, players also have to make a stand and demand to know exactly what they are putting in their bodies.

"Many of them are young and naive and happy to do as they are told, but they need to know exactly what they are taking because their futures could depend on it."

Tredrea said he trusted the Power's doctors Peter Barnes and Mark Fisher to make the right calls on his body from 1997 to 2010.

But he said that with the influx of so-called miracle supplements and clubs desperate to find any competitive edge they can, players can easily be led astray - inside and outside a club.

Tredrea revealed on Triple M radio yesterday that he wasn't far off taking a banned substance during his playing days.

"I was offered performance enhancing drugs by someone exterior to the football club," Tredrea said.

"But I went and got it tested and came back with three illegal drugs in it."

As the Bombers scandal continued to unfold:

PORT said its former Bombers Angus Monfries and Henry Slattery would "co-operate fully" with the AFL and ASADA investigations.

Monfries kicked 165 goals in 150 games for Essendon before joining the Power at the end of last season as its key off-season recruit. Like Slattery, who has joined Port's SANFL club the Magpies, Monfries was with the Bombers last year, the period now under investigation.

COLLINGWOOD captain Nick Maxwell said players would now be more vigilant when taking supplements.

FORMER Essendon coach Kevin Sheedy welcomed the joint investigation into his old club, saying he expects it will lead to tighter sports science oversight in the league.

CARLTON coach Mick Malthouse said he hoped sports scientists would not be given a bad name because "99 per cent of them are absolutely straight, abide by the rules and do everything right". "And we need them because most are people of integrity who make sure the players' health and longevity is assured," he said.

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